Image processing apparatus and method

ABSTRACT

If gamut mapping (hue restoration) defined by one Lab color space is applied in color matching under different reference white points, the human vision perceives the hue as inconsistent. In view of this, input data which is dependent on a color space of an input device is converted by the conversion LUT  11  to color space data which is independent of any devices, based on a viewing condition at the time of viewing an input original. The data is converted to data in the human color perception space by the forward converter  12 , then subjected to gamut mapping, and converted back to data in the color space independent of any devices by the inverse converter  15 , based on a viewing condition at the time of viewing an output original. Then, the data is converted to output data in a color space which is dependent on an output device by the conversion LUT  16.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 09/358,407, filedJul. 22, 1999, the entire content of which is hereby incorporated hereinby reference.

BACKGROUND OF THE INVENTION

The present invention relates to an image processing apparatus andmethod, and more particularly, to an image processing apparatus andmethod for performing color matching according to ambient light.

FIG. 1 is a conceptual view of general color matching.

Input RGB data is converted by an input profile to XYZ data of a colorspace which does not depend on any devices. Since an output devicecannot express colors outside the color reproduction range of the outputdevice, gamut mapping is performed on the inputted data, which has beenconverted to the data in the device-independent color space, such thatall colors of the inputted data fall within the color reproduction rangeof the output device. After the gamut mapping is performed, the inputteddata is converted from the device-independent color space to CMYK dataof a color space which is dependent on the output device.

In color matching, a reference white point and ambient light are fixed.For instance, according to a profile specified by the InternationalColor Consortium (ICC), Profile Connection Space (PCS) for associatingprofiles uses XYZ values or Lab values based on D50 characteristic.Therefore, correct color reproduction is guaranteed when an inputtedoriginal document and a printout are viewed under an illuminant of D50characteristic. Under an illuminant of other characteristics, correctcolor reproduction is not guaranteed.

When a sample (e.g., an image) is viewed under different illuminants,XYZ values of the viewed sample naturally vary. The XYZ values undervarious illuminants are predicted by conversion methods such as (1)ratio conversion, (2) Von Kries conversion, and (3) prediction formulausing a color perception model.

In the ratio conversion method, XYZ values under a reference white pointW1 are converted to XYZ values under a reference white point W2 at aratio of W2/W1. If this conversion method is applied to the Lab uniformcolor space, the Lab values under W1 become equal to the Lab valuesunder W2. Assuming that XYZ values of a sample under W1(Xw1, Yw1, Zw1)are (X1, Y1, Z1) and XYZ values of the sample under W2(Xw2, Yw2, Zw2)are (X2, Y2, Z2), the following relations are obtained by the ratioconversion:

$\begin{matrix}\left. \begin{matrix}{{X2} = {\frac{Xw2}{Xw1}{X1}}} \\{{Y2} = {\frac{Yw2}{Yw1}{Y1}}} \\{{Z2} = {\frac{Zw2}{Zw1}{Z1}}}\end{matrix} \right\} & (1)\end{matrix}$

According to the Von Kries conversion, XYZ values under the referencewhite point W1 are converted to XYZ values under the reference whitepoint W2 at a ratio of W2′/W1′ in a human color perception space PQR. Ifthis conversion method is applied to the Lab uniform color space, theLab values under W1 do not become equal to the Lab values under W2.Assuming that XYZ values of a sample under W1(Xw1, Yw1, Zw1) are (X1,Y1, Z1) and XYZ values of the sample under W2(Xw2, Yw2, Zw2) are (X2,Y2, Z2), the following relations are obtained by Von Kries conversion:

$\begin{matrix}{\begin{bmatrix}{X2} \\{Y2} \\{Z2}\end{bmatrix} = {{{\begin{bmatrix}\; \\{inv\_ Mat} \\\;\end{bmatrix}\begin{bmatrix}\frac{P_{w2}}{P_{w1}} & 0 & 0 \\0 & \frac{Q_{w2}}{Q_{w1}} & 0 \\0 & 0 & \frac{R_{w2}}{R_{w1}}\end{bmatrix}}\lbrack{Mat}\rbrack}\begin{bmatrix}{X1} \\{Y1} \\{Z1}\end{bmatrix}}} & (2)\end{matrix}$where

$\begin{matrix}{{\begin{bmatrix}{Pw2} \\{Qw2} \\{Rw2}\end{bmatrix} = {\begin{bmatrix}\; \\{Mat} \\\;\end{bmatrix}\begin{bmatrix}{Xw2} \\{Yw2} \\{Zw2}\end{bmatrix}}}\mspace{220mu}} & (3) \\{{\begin{bmatrix}{Pw1} \\{Qw1} \\{Rw1}\end{bmatrix} = {\begin{bmatrix}\; \\{Mat} \\\;\end{bmatrix}\begin{bmatrix}{Xw1} \\{Yw1} \\{Zw1}\end{bmatrix}}}\mspace{225mu}} & (4) \\{\begin{bmatrix}\; \\{inv\_ Mat} \\\;\end{bmatrix} = \begin{bmatrix}1.85995 & {- 1.12939} & 0.21990 \\0.36119 & 0.63881 & 0 \\0 & 0 & 1.08906\end{bmatrix}} & (5) \\{\;{\begin{bmatrix}\; \\{Mat} \\\;\end{bmatrix} = \begin{bmatrix}0.44024 & 0.70760 & {- 0.08081} \\{- 0.22630} & 1.16532 & 0.04570 \\0 & 0 & 0.91822\end{bmatrix}}\mspace{45mu}} & (6)\end{matrix}$

To convert XYZ values under a viewing condition VC1 (including W1) toXYZ values under a viewing condition VC2 (including W2), the predictionformula using a color perception model, which is a conversion methodsuch as CIE CAM 97s using the human color perception space QMH (or JCH)is employed. Herein, Q for QMH represents brightness, M representscolorfulness, and H represents hue quadrature or hue angle. J for JCHrepresents lightness, C represents chroma, and H represents huequadrature or hue angle. If this conversion method is applied to the Labuniform color space, the Lab values under W1 are not equal to the Labvalues under W2, as similar to the case of the Von Kries conversion.Assuming that XYZ values of a sample under W1(Xw1, Yw1 Zw1) are (X1, Y1,Z1) and XYZ values of the sample under W2(Xw2, Yw2, Zw2) are (X2, Y2,Z2), the Von Kries conversion performs the following conversion:

-   -   (X1, Y1, Z1)→[forward conversion of CIE CAM97s]→(Q, M, H) or (J,        C, H)→[inverse conversion of CIE CAM97s] (X2, Y2, Z2)

In other words, if it is assumed that XYZ values under a reference whitepoint which varies depending on a ratio conversion can be converted, thecontour lines of hue in the Lab color spaces under various referencewhite points are always the same. However, if human color perception istaken into consideration, such as the Von Kries conversion or predictionformula using a color perception model, the contour lines of hue in theLab color spaces under different reference white points vary dependingon the reference white points.

Because of the above reason, if gamut mapping (hue restoration) definedunder one Lab color space is applied to color matching under differentreference white points, the human vision perceives the hue asinconsistent.

Moreover, in the current ICC profile, since the PCS is limited to XYZvalues or Lab values based on D50 characteristic, color matchingcorresponding to ambient light cannot be performed.

SUMMARY OF THE INVENTION

The present invention is made in consideration of the above situation,and has as its object to provide an image processing apparatus andmethod for performing excellent color matching under different viewingconditions.

In order to attain the above object, the present invention provides animage processing method for performing color process based on a colorappearance model, the image processing method comprising the steps of:inputting location information which relates to a positional relationbetween a viewing subject in a data source side and a viewing subject ina data destination side; and controlling the color process based on theinputted location information.

Another object of the present invention is to provide an imageprocessing apparatus and method for enabling a user to readily set aviewing condition.

In order to attain the above object, the present invention provides animage processing method having a user interface for manually inputtinglocation information which relates to a positional relation between aviewing subject in a data source side and a viewing subject in a datadestination side, and a user interface for manually inputting viewinginformation which relates to a viewing condition, for performing colorprocess on input image data based on a color appearance model, the imageprocessing method comprising the step of controlling the color processbased on the inputted location information and viewing information.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the description, serve to explain the principles of theinvention.

FIG. 1 is a conceptual view of color matching;

FIG. 2 is an explanatory view showing a concept of the presentinvention;

FIG. 3 is a block diagram showing the functional configuration of afirst embodiment of the present invention;

FIG. 4 is a flowchart showing the process of reconstructing a conversionLUT which corresponds to an ambient light;

FIG. 5 is a flowchart showing the process of updating a conversion LUTso as to correspond to an ambient light;

FIG. 6 is a flowchart showing the process of performing gamut mapping inthe color space JCH or QMH;

FIG. 7 shows a dodecahedron for approximating a color reproductionrange;

FIGS. 8A and 8B are conceptual views of gamut mapping in the JCH colorperception space;

FIGS. 9A and 9B are conceptual views of gamut mapping in the QMH colorperception space;

FIGS. 10A and 10B are conceptual views of gamut mapping performedbetween different devices;

FIG. 11 is a flowchart showing the process of reconstructing aconversion LUT which corresponds to an ambient light;

FIG. 12 is a conceptual view of color matching processing;

FIG. 13 is a conceptual view of color matching according to a secondembodiment of the present invention;

FIG. 14 is a flowchart showing the process of performing gamut mappingin the color space JCH or QMH according to the second embodiment;

FIG. 15 is a flowchart showing the process of reconstructing aconversion LUT which corresponds to an ambient light according to thesecond embodiment;

FIG. 16 is a conceptual view of color matching according to a thirdembodiment of the present invention;

FIG. 17 is a flowchart showing the process of updating a conversion LUTso as to correspond to an ambient light in the second embodiment;

FIG. 18 is a block diagram showing a construction of an apparatus whichrealizes the functional configuration shown in FIG. 3;

FIG. 19 is an explanatory block diagram of a color appearance model usedin the embodiments of the present invention;

FIG. 20 is a conceptual view of a profile storing XYZ values of a whitepoint under different illuminants, device-dependent RGB values of acolor target, XYZ values corresponding to the color target underrespective illuminants;

FIG. 21 shows a spectral distribution of a standard illuminant;

FIG. 22 is a flowchart showing the process of conjecturing acolorimetric value from the colorimetric data for plural illuminants;

FIG. 23 shows an example in which a LUT, provided for mutuallyconverting a device-independent color space under a viewing condition toa device-dependent color space, is stored in the ICC profile;

FIG. 24 is a flowchart showing caching processing;

FIG. 25 shows an example of a Graphic User Interface (GUI) for setting aparameter of a viewing condition according to a sixth embodiment of thepresent invention;

FIG. 26 shows an example of a GUI which enables setting of a user level;and

FIG. 27 shows the GUI of FIG. 26, whose user level is set in“professional level”.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the image processing apparatus and method aswell as the profile generating method according to the present inventionwill be described in detail with reference to the accompanying drawings.

First, a color appearance model used in the following embodiments isdescribed with reference to FIG. 19.

A color perceived by human visual system is different depending onconditions, such as the difference in lighting or a background on whicha stimulus as a viewing subject is placed, even if the characteristic oflight entering the eye is the same.

For instance, a white color, illuminated by an incandescent lamp, is notperceived as red as the characteristic of light entering the eye, but isperceived as white. A white color placed on a black background isperceived brighter than a white color placed on a bright background. Theformer phenomenon is known as chromatic adaptation and the latter isknown as a contrast. In view of this, colors must be displayed not bythe XYZ color system, but by the volume corresponding to a physiologicalactivity level of visual cells distributed on the retina. For thispurpose, a color appearance model has been developed. The CIE(Commission Internationale de l'Eclairage) recommends using the CIECAM97s. This color appearance model utilizes color perceptioncorrelation values, which are H (hue), J (lightness) and C (chroma), orH (hue), Q (brightness) and M (colorfulness), as physiological threeprimary colors of color vision, and is considered as a color displaymethod which do not depend upon viewing conditions. By reproducingcolors so as to match the values of H, J and C or H, Q and M betweendevices, it is possible to solve the problem of different viewingconditions in an input image and output image.

Description will be provided with reference to FIG. 19 for theprocessing of forward conversion of the color appearance model CIECAM97s, for performing correction processing (conversion from XYZ to JCHor QMH) in accordance with a viewing condition at the time of viewing animage to be inputted.

In step S160, LA indicative of a luminance of an adaptive visual field(cd/m²) (normally, 20% of white luminance in the adaptive visual fieldis selected), XYZ indicative of relative tristimulus values of a sampleunder an illuminant condition, XwYwZw indicative of relative tristimulusvalues of a white light under the illuminant condition, and Ybindicative of a relative luminance of a background under the illuminantcondition are set as the viewing condition information of an image to beinputted. Based on the type of viewing condition specified in step S180,a constant c indicative of an impact of surround, a chromatic inductionfactor Nc, a lightness contrast factor FLL, and an factor for degree ofadaptation F are set as the viewing condition information of the inputimage in step S170.

Based on the input image viewing condition information set in steps S160and S170, the following processing is performed on the XYZ representingan input image.

First, the XYZ are converted based on the Bradford's three primarycolors, which are considered as human physiological three primarycolors, to obtain RGB corresponding to Bradford's cone response (stepS100). Since human vision does not always completely adapt to theviewing illuminant, a variable D indicative of adaptability is obtainedbased on a luminance level and a viewing condition (LA and F). Based onthe obtained variable D and XwYwZw, incomplete adaptation processing isperformed on RGB to be converted to RcGcBc (step S110).

Next, RcGcBc is converted based on Hunt-Pointer-Estevez's three primarycolors, which are considered as human physiological three primarycolors, to obtain R′G′B′ corresponding to Hunt-Pointer-Estevez's coneresponse (step S120). The adaptability of R′G′B′ is estimated by astimulus intensity level to obtain R′aG′aB′a corresponding to an adaptedcone response which corresponds to both the sample and white (stepS130). Note that in step S130, non-linear response compression isperformed by using a variable FL which is calculated based on theluminance LA of the adaptive visual field.

Then, to obtain the correlation between a color perception and the XYZ,the following processing is performed.

Opposite color responses a and b of red-green and yellow-blue arecalculated from R′aG′aB′a (step S140), and a hue H is calculated fromthe opposite color responses a and b and a eccentricity factor (stepS150).

Then, a background inducing coefficient n is calculated from Yw and therelative luminance Yb of the background. By using the backgroundinducing coefficient n, achromatic color responses A and Aw with respectto both the sample and white are calculated (step S190). Lightness J iscalculated by using a coefficient z, calculated from the backgroundinducing coefficient n and lightness contrast factor FLL, and theachromatic color responses A and Aw as well as the impact of surroundconstant c (step S151). A saturation S is calculated from the chromaticinduction factor NL (step S153), then from the saturation S andlightness J, a chroma C is calculated (step S152), and a brightness Q iscalculated from the lightness J and achromatic color response Aw forwhite (step S154).

A colorfulness M is calculated from the variable FL and impact ofsurround constant c (step S155).

<First Embodiment>

Description is provided for the first embodiment in which a profile isdynamically changed in accordance with a viewing condition.

Referring to FIG. 2 which describes a concept of the present invention,reference numeral 11 denotes a conversion matrix or a conversion lookuptable (LUT) for converting data which is dependent on an input device(hereinafter referred to as input-device-dependent data) to data of thedevice-independent color space (hereinafter referred to asinput-independent data), which accords to a white point of ambient lightat the time of viewing an image formed on an original. Reference numeral12 denotes a forward converter (CAM) of a color appearance model forconverting data, obtained from the conversion LUT 11, to human colorperception color space JCh or QMh. Reference numeral 13 denotes arelative color perception space JCh (or JCH) relative to the referencewhite of an ambient light; and 14, an absolute color perception spaceQMh (or QMH) whose size changes in accordance with an illuminance level.Reference numeral 15 denotes an inverse converter of a color appearancemodel for converting data of the human's color perception space JCh orQMh to data of the device independent color space (hereinafter referredto as output-independent data), which accords to a white point ofambient light at the time of viewing an image formed on a printout.Reference numeral 16 denotes a conversion LUT for converting data,obtained from the inverse converter 15, to data which is dependent on anoutput device (hereinafter referred to as output-device-dependent data).

Generally, the white point of ambient light under a viewing condition isdifferent from a white point of the standard illuminant at the time ofcolorimetry of a color target or color patch or the like. For instance,the standard illuminant used at the time of colorimetry is D50 or D65,but an ambient light for actually viewing an image is not always D50 orD65 in a light booth. An illumination light from an incandescent lamp orfluorescent light, or a combination of illumination light and sunlightare often used as the ambient light in which the image is actuallyviewed. In the following description, although an illuminantcharacteristic of an ambient light under a viewing condition is assumedas D50, D65 and D93 to simplify the description, in reality, XYZ valuesof a white point on a medium is set as a white point.

FIG. 3 is a block diagram showing a functional configuration of thepresent embodiment. In FIG. 3, reference numeral 41 denotes a datageneration portion for generating data, which is dependent on theviewing condition 1 of a data input side, based on an input profile 42and the viewing condition 1. Reference numeral 43 denotes a gamutmapping mode selection portion for selecting whether the gamut mappingis performed in the JCH color perception space or in the QMH colorperception space in accordance with designation by a user or designationby the profile. Reference numerals 44 and 45 denote gamut mappingportions respectively for performing gamut mapping on data in the JCH orQMH color perception space in accordance with an output profile 46.Reference numeral 47 denotes a data generation portion for generatingdata, which is dependent on a viewing condition 2 of an image outputside, based on the output profile 46 and viewing condition 2. Referencenumeral 48 denotes a color matching portion for performing colormatching by utilizing the data which is dependent on the viewingcondition 1, the gamut mapped data, the data which is dependent on theviewing condition 2, and color appearance model.

FIG. 18 is a block diagram showing a construction of an apparatus whichrealizes the functional configuration shown in FIG. 3. It goes withoutsaying that the apparatus shown in FIG. 18 is realized by supplying ageneral computer apparatus, such as a personal computer or the like,with software which realizes the function shown in FIG. 3. In this case,the software which realizes the function of the present embodiment maybe included in the Operating System (OS) which is the basic systemsoftware of the computer apparatus, or may be provided, for instance, asa driver software of an input/output device independently of the OS.

In FIG. 18, a CPU 100 controls operation of the entire apparatusaccording to a program stored in a ROM 101 and hard disk (HD) 106 andthe like, by utilizing a RAM 102 as a work memory, and executes variousprocessing including the processing related to the above-described colormatching. An input interface 103 is provided to connect an input device104; a hard disk interface 105 is provided to connect the HD 106; avideo interface 107 is provided to connect a monitor 108; and an outputinterface 109 is provided to connect an output device 110.

Note that the input device according to the present embodiment includesan image sensing device such as a digital still camera or a digitalvideo camera or the like, and various image input devices including animage reader such as an image scanner or film scanner or the like. Theoutput device according to the present embodiment includes a colormonitor such as a CRT or LCD or the like, and an image output devicesuch as a color printer or film recorder or the like.

A general interface is utilized as the interface of the presentembodiment. Depending on the usage purpose, a serial interface such asRS232C, RS422 or the like, a serial bus interface such as IEEE 1394,Universal Serial Bus (USB) or the like, and a parallel interface such asSCSI, GPIB, centronics or the like, are applicable.

Input/output profiles for color matching are stored in the HD 106.However, the storage medium is not limited to hard disk, but may be anoptical disk such as a magneto-optical disk (MO) or the like.

Hereinafter, description is provided for an example of performing colormatching by using the input/output profiles.

[Generating Data Dependent on Viewing Condition 1]

The conversion LUT 11 is generated by the data generation portion 41.Methods of generating the conversion LUT 11 include: a method ofreconstructing the conversion LUT 11 so as to correspond to an ambientlight, based on a relation between XYZ values (or Lab values) of a colortarget and RGB values of an input device as shown in FIG. 4; and amethod of updating a conversion LUT stored in the input profile 42,which is provided for converting an RGB space dependent on a device toXYZ color space, to the conversion LUT 11 which corresponds to theambient light.

FIG. 4 is a flowchart showing the process of reconstructing theconversion LUT 11 which corresponds to an ambient light.

To reconstruct the conversion LUT 11 so as to correspond to an ambientlight, a profile designated by a user is read from the input profile 42in step S51. XYZ values (or Lab values) of the color target andXYZ-to-RGB relation data, which associates the XYZ values with RGBvalues for a case of reading the color target by an input device, arestored in advance in the profile. The XYZ-to-RGB relation data isobtained from the profile in step S52. Since the profile includes aviewing condition 1, the viewing condition 1 is obtained from theprofile in step S53.

The XYZ values of the XYZ-to-RGB relation data, obtained in step S52,employ as a reference, D50 or D65 indicative of a reference light at thetime of colorimetry of the color target. Therefore, the XYZ values ofthe colorimetric illuminant reference must be corrected to XYZ values ofan ambient light reference. In step S54, by using the color appearancemodel, the XYZ values of the colorimetric illuminant reference areconverted to the color perception space JCH based on a colorimetriccondition, i.e., the white point of D50 illuminant, an illuminancelevel, and the state of ambient light, and then the converted values inthe color perception space JCH are converted back to XYZ values based onthe viewing condition 1 different from the colorimetric condition, e.g.,the white point of D65 illuminant, an illuminance level, and the stateof ambient light. By this, XYZ values of the ambient light reference areobtained. In the foregoing manner, the relation between XYZ values ofthe ambient light reference and device RGB values is obtained. In stepS55, an RGB-to-XYZ conversion matrix is generated based on theRGB-to-XYZ relation data and optimized by repetition or the like,thereby obtaining the conversion LUT 11 which corresponds to the viewingcondition 1.

FIG. 5 is a flowchart showing the process of updating the conversionLUT, stored in the input profile 42, to the conversion LUT 11 whichcorresponds to an ambient light. Note that the steps in FIG. 5 executingthe same processing as those in FIG. 4 have the same reference stepnumber, and detailed description thereof is omitted.

Generally in the ICC profile for an input device, a conversion matrix(colorant Tag) for performing RGB-to-XYZ conversion, or a conversion LUT(AtoB0 Tag) is stored. Thus, the RGB-to-XYZ relation data is obtainedfrom the profile in step S62.

In step S54, the relation between XYZ values of the ambient lightreference and device RGB values is obtained. Then in step S66, theconversion matrix (colorant Tag) or conversion LUT (AtoB0 Tag) in theprofile is updated. As a result, a conversion LUT, updated to theconversion LUT 11 corresponding to the viewing condition 1, is obtained.

Moreover, although FIGS. 4 and 5 provide an example of utilizing theRGB-to-XYZ relation data, the present invention is not limited to this,but may utilize other device-independent color data such as RGB-to-Labrelation data.

[Selecting Gamut Mapping Mode and Performing Gamut Mapping]

A gamut mapping mode is selected by a user through a user interface, orautomatically selected by Rendering Intent included in the header of asource profile. The following selection is made in the automaticselection according to the profile.

Perceptual—gamut mapping mode in JCH color space

Relative Colorimetric—gamut mapping mode in JCH color space

Saturation—gamut mapping mode in JCH color space

Absolute Colorimetric—gamut mapping mode in QMH color space

In other words, in a case of relative color matching, JCH space 13 isselected, while in a case of absolute color matching, QMH space 14 isselected.

FIG. 6 is a flowchart showing the process of performing the gamutmapping in the color perception space JCH 13 or color perception spaceQMH 14.

In order to perform the gamut mapping in a color perception space, aprofile designated by a user is read from the output profile 46 in stepS81.

Generally in the ICC profile for an output device, a judgment LUT (gamutTag), to which XYZ values or Lab values are inputted, is stored in orderto judge inside or outside the color reproduction range (hereinafterreferred to as inside/outside judgment of the color reproduction range).However, because the XYZ values employ D50 or D65 which is thecharacteristic of colorimetric illuminant as a reference, the XYZ valuescannot be used directly to make judgment of inside/outside the colorreproduction range according to an ambient light. Therefore, instead ofusing the judgment LUT (gamut Tag) which judges inside/outside the colorreproduction range, CMYK-to-XYZ relation data is obtained in step S82from the conversion LUT (AtoB0 Tag or the like), stored in the profilefor CMYK-to-XYZ conversion. Since the profile includes the viewingcondition 2, the viewing condition 2 is obtained from the profile instep S83.

The XYZ values of the CMYK-to-XYZ relation data, obtained in step S82,employ as a reference, D50 or D65 indicative of a colorimetric light.Therefore, the XYZ values of the colorimetric illuminant reference mustbe corrected to XYZ values of an ambient light reference. In step S84,by using the color appearance model, the XYZ values of the colorimetricilluminant reference are converted to the color perception space JCHbased on a colorimetric condition, i.e., the white point of D50illuminant, an illuminance level, and the state of ambient light, andthen the converted values in the color perception space JCH areconverted back to XYZ values based on the viewing condition 2 differentfrom the colorimetric condition, e.g., the white point of D65illuminant, an illuminance level, and the state of ambient light. Bythis, XYZ values of the ambient light reference are obtained. In theforegoing manner, the relation between the device CMYK values and XYZvalues of the ambient light reference is obtained in step S84. In stepS85, a color reproduction range of an output device in the JCH or QMHcolor space is obtained based on the CMYK-to-ambient-light-XYZ relationdata obtained in step S84.

The color reproduction range of an output device in the JCH or QMH colorspace is obtained as follows. XYZ values of an ambient light referenceon the following eight points, shown as an example, are obtained byusing the CMYK-to-ambient-light-XYZ relation data obtained in step S84.

Red (C: 0%, M: 100%, Y: 100%, K: 0%) Yellow (C: 0%, M: 0%, Y: 100%, K:0%) Green (C: 100%, M: 0%, Y: 100%, K: 0%) Cyan (C: 100%, M: 0%, Y: 0%,K: 0%) Blue (C: 100%, M: 100%, Y: 0%, K: 0%) Magenta (C: 0%, M: 100%, Y:0%, K: 0%) White (C: 0%, M: 0%, Y: 0%, K: 0%) Black (C: 0%, M: 0%, Y:0%, K: 100%)Then, the obtained XYZ values are converted to coordinate values in thecolor perception space JCH or QMH based on the viewing condition 2 byusing the color appearance model. By this, the color reproduction rangeof the output device can be approximated by a dodecahedron shown in FIG.7.

In the color reproduction range approximated by the dodecahedron, forinstance, if an intermediate point between White and Black on anachromatic color axis and a point represented by JCH values or QMHvalues of an input color signal subjected to inside/outside judgmentexist in the same side, it is judged that the input color signal isinside the color reproduction range, while if these points exist in theopposite sides, it is judged that the input color signal is outside thecolor reproduction range.

Based on the result of inside/outside judgment of the color reproductionrange in step S85, the gamut mapping is performed in step S86. FIGS. 8Aand 8B are conceptual views of the gamut mapping in the JCH colorperception space. FIGS. 9A and 9B are conceptual views of the gamutmapping in the QMH color perception space. If an input color signal isjudged as being outside the color reproduction range of the outputdevice in the aforementioned inside/outside judgment, the input colorsignal is mapped in the color reproduction range such that a hue angle h(or H) is preserved in the JCH color perception space or QMH colorperception space. The mapping result is stored in the LUT for the JCHcolor perception space in a case of relative color matching, or storedin the LUT for the QMH color perception space in a case of absolutecolor matching.

FIGS. 10A and 10B are conceptual views of the gamut mapping performedbetween different devices. In the drawings, the broken lines indicate acolor reproduction range of an input device, and the solid linesindicate a color reproduction range of an output device. In the JCHcolor perception space, the level of J (lightness) is normalizedrespectively by illuminant white points under the viewing conditions 1and 2 (hereinafter referred to as “white point 1” and “white point 2”).Thus, J does not depend on the illuminance levels of the viewingconditions 1 and 2 (hereinafter referred to as “illuminance level 1” and“illuminance level 2”). On the other hand, in the QMH color perceptionspace, the level of Q (brightness) changes in accordance with theilluminance levels 1 and 2. Therefore, in the relative color matching,the white point 1 becomes the white point 2. Meanwhile in the absolutecolor matching, if illuminance level 1>illuminance level 2, the whitepoint 1 is mapped to the white point 2. If illuminance level1<illuminance level 2, the white point 1 is outputted in gray colorbecause the white point 1 is lower than white point 2.

[Generating Data Dependent on Viewing Condition 2]

Next, the conversion LUT 16 is generated by the data generation portion47.

FIG. 11 is a flowchart showing the process of reconstructing theconversion LUT 16 which corresponds to an ambient light.

Generally in the ICC profile for an output device, a LUT (BtoA0 Tag orthe like) for converting XYZ or Lab values to device CMYK or RGB valuesis stored in the form including information of the gamut mapping.However, since the XYZ values inputted to the LUT employ D50 or D65 as areference, the XYZ values cannot be directly used as a conversion LUTwhich corresponds to an ambient light.

As similar to the gamut mapping processing, a conversion LUT (AtoB0 Tagor the like) for performing CMYK-to-XYZ conversion is read from theoutput profile 46 in step S71, and CMYK-to-XYZ relation data is obtainedfrom the conversion LUT in step S72. Note that CMYK values of theCMYK-to-XYZ relation data may be other device-dependent colors such asRGB values or the like, and XYZ values may be other device-independentcolors such as Lab values or the like. In step S73, the viewingcondition 2 is obtained from the output profile 46 which stores theviewing condition 2 in advance.

The XYZ values of the obtained CMYK-to-XYZ relation data employ D50 orD65 as a reference. Therefore, the XYZ values of the colorimetricilluminant reference must be corrected to XYZ values of an ambient lightreference in step S74. More specifically, by using the color appearancemodel, the XYZ values of the colorimetric illuminant reference areconverted to the color perception space JCH based on a colorimetriccondition, i.e., the white point of D50 illuminant, an illuminancelevel, and the state of ambient light, and then the converted values inthe color perception space JCH are converted back to XYZ values based onthe viewing condition 2 different from the colorimetric condition, e.g.,the white point of D65 illuminant, an illuminance level, and the stateof ambient light. By this, XYZ values of the ambient light reference areobtained. In the foregoing manner, the relation between the device CMYKvalues and XYZ values of the ambient light reference is obtained. Instep S75, ambient light XYZ-to-CMYK relation data is optimized byrepetition or the like, using the CMYK-to-ambient-light-XYZ relationdata, thereby obtaining the conversion LUT 16 which corresponds to adesired ambient light.

[Executing Color Matching]

FIG. 12 is a conceptual view of color matching processing. Referencenumeral 11 denotes a conversion LUT generated based on the viewingcondition 1 by the data generation portion 41; 132, a LUT generated inthe JCH color space by the gamut mapping portion 44; 133, a LUTgenerated in QMH color space by the gamut mapping portion 45; and 16, aconversion LUT generated based on the viewing condition 2 by the datageneration portion 47.

RGB or CMYK input color signals are converted by the conversion LUT 11from the input-device-dependent color signals to XYZ signals which aredevice-independent signals under the viewing condition 1. Next, the XYZsignals are converted by color appearance model forward converters 134and 135 to perception signals JCH or QMH, based on the viewing condition1, such as the white point of D50 illuminant, an illuminance level, andthe state of ambient light. In a case of relative color matching, JCHspace is selected, while in a case of absolute color matching, QMH spaceis selected.

The color perception signals JCH and QMH are mapped to a colorreproduction range of the output device by the LUT 132 and 133. Thecolor perception signals JCH and QMH, where the gamut mapping has beenperformed, are converted by color appearance model inverse converters136 and 137 to XYZ signals which are device-independent signals underthe viewing condition 2, based on the viewing condition 2, such as thewhite point of D65 illuminant, an illuminance level, and the state ofambient light. Then, XYZ signals are converted tooutput-device-dependent color signals under the viewing condition 2 bythe conversion LUT 134.

The RGB or CMYK signals obtained by the above processing are sent to theoutput device, and an image represented by the color signals is printed.When the printout is viewed under the viewing condition 2, the colors ofthe printout are perceived as the same as the original document viewedunder the viewing condition 1.

<Second Embodiment>

Hereinafter, described as a second embodiment is an example of colormatching utilizing an input profile and monitor profile shown in FIG.13. Note that the construction and processing similar to that of thefirst embodiment will not be described in detail.

[Generating Data Dependent on Viewing Condition 1]

A conversion LUT 21 shown in FIG. 13 is generated by the data generationportion 41 in the same method as described in the first embodiment,i.e., the processing shown in FIGS. 4 and 5.

[Selecting Gamut Mapping Mode and Performing Gamut Mapping]

Since the selection of a gamut mapping mode is performed in the samemanner as that of the first embodiment, detailed description will not beprovided.

FIG. 14 is a flowchart showing the process of performing the gamutmapping in the color perception space JCH 23 or color perception spaceQMH 24 shown in FIG. 13.

To perform the gamut mapping in a color perception space, a profiledesignated by a user is read from a monitor profile 142 in step S141.

Generally in the ICC profile for a monitor device, a judgment LUT (gamutTag), to which XYZ values or Lab values are inputted, is often stored inorder to make inside/outside judgement of the color reproduction range.However, because the XYZ values employ D50 or D65 which is thecharacteristic of colorimetric illuminant as a reference, the XYZ valuescannot be used directly to make judgment of inside/outside the colorreproduction range according to an ambient light. Therefore, instead ofusing the judgment LUT (gamut Tag) which judges inside/outside the colorreproduction range, RGB-to-XYZ relation data is obtained in step S142from a conversion matrix (colorant Tag) or conversion LUT (AtoB0 Tag orthe like), stored in the profile for RGB-to-XYZ conversion. Since themonitor profile includes a monitor viewing condition 4, the viewingcondition 4 is obtained from the monitor profile in step S143. Note thatXYZ values of the RGB-to-XYZ relation data may be otherdevice-independent color values such as Lab values.

The XYZ values of the RGB-to-XYZ relation data, obtained in step S142,employ D50 indicative of a colorimetric light, or a monitor's whitepoint as a reference. Therefore, the XYZ values of the colorimetricilluminant reference must be corrected to XYZ values of an ambient lightreference. In step S144, by using the color appearance model, the XYZvalues of the colorimetric illuminant reference are converted to thecolor perception space JCH based on a colorimetric condition, i.e., thewhite point of D50 illuminant, a luminance level, and the state ofambient light, and then the converted values in the color perceptionspace JCH are converted back to XYZ values based on the viewingcondition 4 different from the colorimetric condition, e.g., the whitepoint of D93 illuminant, a luminance level, and the state of ambientlight. By this, XYZ values of the ambient light reference are obtained.In the foregoing manner, the relation between the device RGB values andXYZ values of the ambient light reference is obtained. In step S145, acolor reproduction range of a monitor device in the JCH or QMH colorspace is obtained.

The color reproduction range of a monitor device is obtained as follows.XYZ values of an ambient light reference on the following eight points,shown as an example, are obtained by the conversion processing of XYZreference condition in step S144.

Red (R: 255, G: 0, B: 0) Yellow (R: 255, G: 255, B: 0) Green (R: 0, G:255, B: 0) Cyan (R: 0, G: 255, B: 255) Blue (R: 0, G: 0, B: 255) Magenta(R: 255, G: 0, B: 255) White (R: 255, G: 255, B: 255) Black (R: 0, G: 0,B: 0)

Then, the obtained XYZ values are converted to coordinate values in thecolor perception space JCH or QMH based on the viewing condition 4 byusing the color appearance model. By this, the color reproduction rangeof the monitor device can be approximated by a dodecahedron shown inFIG. 7. In the color reproduction range approximated by thedodecahedron, for instance, if an intermediate point between White andBlack on an achromatic color axis and a point represented by JCH valuesor QMH values of an input color signal subjected to inside/outsidejudgment exist in the same side, it is judged that the input colorsignal is inside the color reproduction range, while if these pointsexist in the opposite sides, it is judged that the input color signal isoutside the color reproduction range.

Based on the result of inside/outside judgment of the color reproductionrange in step S145, the gamut mapping is performed in step S146. FIGS.8A and 8B are conceptual views of the gamut mapping in the JCH colorperception space. FIGS. 9A and 9B are conceptual views of the gamutmapping in the QMH color perception space. If an input color signal isjudged as being outside the color reproduction range of the outputdevice in the aforementioned inside/outside judgment, the input colorsignal is mapped in the color reproduction range such that a hue angle h(or H) is preserved in the JCH color perception space or QMH colorperception space. The color reproduction range obtained in step S146 isstored in the LUT for the JCH color perception space in a case ofrelative color matching, or stored in the LUT for the QMH colorperception space in a case of absolute color matching.

FIGS. 10A and 10B are conceptual views of the gamut mapping performedbetween different devices. In the drawings, the broken lines indicate acolor reproduction range of an input device, and the solid linesindicate a color reproduction range of an output device. In the JCHcolor perception space, the level of J (lightness) is normalizedrespectively by illuminant white points under the viewing conditions 1and 4 (hereinafter referred to as “white point 1” and “white point 4”).Thus, J does not depend on the illuminance level of the viewingcondition 1 and luminance level of the viewing condition 4 (hereinafterreferred to as “illuminance level 1” and “luminance level 4”). On theother hand, in the QMH color perception space, the level of Q(brightness) changes in accordance with the illuminance level 1 andluminance level 4. Therefore, in the relative color matching, the whitepoint 1 becomes the white point 4. Meanwhile in the absolute colormatching, if illuminance level 1>luminance level 4, the white point 1 ismapped to the white point 4. If illuminance level 1<luminance level 4,the white point 1 is outputted in gray color because the white point 1is lower than white point 4.

[Generating Data Dependent on Viewing Condition 4]

Next, the conversion LUT 26 shown in FIG. 13 is generated by the datageneration portion 47.

FIG. 15 is a flowchart showing the process of reconstructing theconversion LUT 26 which corresponds to an ambient light.

In the ICC profile for a monitor device, there are cases in which a LUT(BtoA0 Tag or the like) for converting XYZ to device RGB values isstored in the form including information of the gamut mapping. However,since the XYZ values inputted to the LUT employ D50 or D65 as areference, the XYZ values cannot be directly used as a conversion LUTwhich corresponds to an ambient light.

As similar to the gamut mapping processing, a conversion matrix(colorant Tag) or a conversion LUT (AtoB0 Tag or the like) forperforming RGB-to-XYZ conversion is read from the monitor profile 142 instep S151, and RGB-to-XYZ relation data is obtained from the conversionLUT in step S152. Note that XYZ values of the RGB-to-XYZ relation datamay be other device-independent color values, such as Lab values or thelike. In step S153, the viewing condition 4 is obtained from the monitorprofile 142 which stores the viewing condition 4 in advance.

The XYZ values of the obtained RGB-to-XYZ relation data employ D50 ormonitor's white point as a reference. Therefore, the XYZ values of thecolorimetric illuminant reference must be corrected to XYZ values of anambient light reference in step S154. More specifically, by using thecolor appearance model, the XYZ values of the colorimetric illuminantreference are converted to the color perception space JCH based on acolorimetric condition (the white point of D50 illuminant, a luminancelevel, and the state of ambient light), and then the converted values inthe color perception space JCH are converted back to XYZ values based onthe viewing condition 4 (the white point of D93 illuminant, a luminancelevel, and the state of ambient light) which is different from thecolorimetric condition. By this, XYZ values of the colorimetricilluminant reference are converted to XYZ values of the ambient lightreference. In the foregoing manner, the relation between the device RGBvalues and XYZ values of the ambient light reference is obtained. Instep S155, the RGB-to-XYZ conversion is formulated into a model such asa conversion matrix and optimized by repetition or the like, therebyobtaining the conversion LUT 26 which corresponds to a desired ambientlight.

[Executing Color Matching]

FIG. 12 is a conceptual view of color matching processing. Referencenumeral 21 denotes a conversion LUT generated based on the viewingcondition 1 by the data generation portion 41; 132, a LUT generated inthe JCH color space by the gamut mapping portion 44; 133, a LUTgenerated in QMH color space by the gamut mapping portion 45; and 26, aconversion LUT generated based on the viewing condition 4 by the datageneration portion 47.

RGB input color signals are converted by the conversion LUT 21 from theinput-device-dependent color signals to XYZ signals which aredevice-independent signals under the viewing condition 1. Next, the XYZsignals are converted by color appearance model forward converters 134and 135 to perception signals JCH or QMH, based on the viewing condition1, such as the white point of D50 illuminant, an illuminance level, andthe state of ambient light. In a case of relative color matching, JCHspace is selected, while in a case of absolute color matching, QMH spaceis selected.

The color perception signals JCH and QMH are mapped to a colorreproduction range of the monitor device by the LUT 132 and 133. Thecolor perception signals JCH and QMH, where the gamut mapping has beenperformed, are converted by color appearance model inverse converters136 and 137 to XYZ signals which are device-independent signals underthe viewing condition 4, based on the viewing condition 4, such as thewhite point of D93 illuminant, a luminance level, and the state ofambient light. Then, XYZ signals are converted tomonitor-device-dependent color signals under the viewing condition 4 bythe conversion LUT 26.

The RGB signals obtained by the above processing are sent to the monitordevice, and an image represented by the color signals is displayed onthe monitor device. When the displayed image is viewed under the viewingcondition 4, the colors of the displayed image are perceived as the sameas the original document viewed under the viewing condition 1.

<Third Embodiment>

Hereinafter, described as a third embodiment is an example of colormatching utilizing a monitor profile and output profile shown in FIG.16. Note that the construction and processing similar to that of thefirst and second embodiments will not be described in detail.

In the ICC profile for a monitor device, a conversion matrix (colorantTag) or a conversion LUT (AtoB0 Tag) for performing RGB-to-XYZconversion is stored. In step S162 in FIG. 17, RGB-to-XYZ relation datais obtained. Since the profile includes the viewing condition 4, theviewing condition 4 is obtained from the profile in step S163. Note thatXYZ values of the RGB-to-XYZ relation data may be otherdevice-independent color values such as Lab values.

The XYZ values of the obtained RGB-to-XYZ relation data employ D50 ormonitor's white point as a reference. Therefore, the XYZ values of thecolorimetric illuminant reference must be corrected to XYZ values of anambient light reference in step S164. More specifically, by using thecolor appearance model, the XYZ values of the colorimetric illuminantreference are converted to the color perception space JCH based on acolorimetric condition (the white point of D50 illuminant, a luminancelevel, and the state of ambient light), and then the converted values inthe color perception space JCH are converted back to XYZ values based onthe viewing condition 4 (the white point of D93 illuminant, a luminancelevel, and the state of ambient light), which is different from thecolorimetric condition. By this, XYZ values of the colorimetricilluminant reference are converted to XYZ values of the ambient lightreference. In the foregoing manner, the relation between the device RGBvalues and XYZ values of the ambient light reference is obtained. Instep S165, the conversion matrix (colorant Tag) or conversion LUT (AtoB0Tag) in the monitor profile 142 is updated, thereby obtaining aconversion LUT 31 which corresponds to a desired ambient light.

[Selecting Gamut Mapping Mode and Performing Gamut Mapping]

Since the selection of a gamut mapping mode is performed in the samemanner as that of the first embodiment, detailed description will not beprovided. Furthermore, since the gamut mapping is also performed in thesame manner as that described in the first embodiment shown in FIG. 6,detailed description will not be provided.

[Generating Data Dependent on Viewing Condition 2]

Next, a conversion LUT 36 is generated by the data generation portion47. Since the processing is the same as that described in the firstembodiment shown in FIG. 11, detailed description will not be provided.

[Executing Color Matching]

FIG. 12 is a conceptual view of color matching processing. Referencenumeral 31 denotes a conversion LUT generated based on the viewingcondition 4 by the data generation portion 41; 132, a LUT generated inthe JCH color space by the gamut mapping portion 44; 133, a LUTgenerated in QMH color space by the gamut mapping portion 45; and 36, aconversion LUT generated based on the viewing condition 2 by the datageneration portion 47.

RGB input color signals are converted by the conversion LUT 31 from themonitor-device-dependent color signals to XYZ signals which aredevice-independent signals under the viewing condition 4. Next, the XYZsignals are converted by color appearance model forward converters 134and 135 to perception signals JCH or QMH, based on the viewing condition4, such as the white point of D93 illuminant, a luminance level, and thestate of ambient light. In a case of relative color matching, JCH spaceis selected, while in a case of absolute color matching, QMH space isselected.

The color perception signals JCH and QMH are mapped to a colorreproduction range of the output device by the LUT 132 and 133. Thecolor perception signals JCH and QMH, where the gamut mapping has beenperformed, are converted by color appearance model inverse converters136 and 137 to XYZ signals which are device-independent signals underthe viewing condition 2, based on the viewing condition 2, such as thewhite point of D65 illuminant, an illumination level, and the state ofambient light. Then, XYZ signals are converted tooutput-device-dependent color signals under the viewing condition 2 bythe conversion LUT 36.

The CMYK signals obtained by the above processing are sent to the outputdevice, and an image represented by the color signals is printed. Whenthe printout is viewed under the viewing condition 2, the colors of theprintout are perceived as the same as the image viewed under the viewingcondition 4.

<Fourth Embodiment>

In each of the foregoing embodiments, descriptions have been providedfor an example in which a color matching module CMM dynamically convertsa profile, which has been generated from a colorimetric value employingD50 and D65 as a reference, into a profile which is dependent on aviewing condition. Instead, by generating a profile which is fixed to aviewing condition in advance, color matching corresponding to an ambientlight can be performed.

Hereinafter described as a fourth embodiment is a method of generating aprofile dependent on a viewing condition for selecting a correspondingprofile from a plurality of profiles respectively corresponding toviewing conditions.

[Generating Profile Dependent on Viewing Condition in Data Source Side]

Data 11 for a conversion LUT, which is dependent on a viewing conditionof the data source side, is generated based on a profile which has beengenerated from a colorimetric value employing D50 or D65 as a reference,by the processing similar to the processing of the data generationportion 41 shown in FIG. 3 for generating data dependent on the viewingcondition of the data source side. Since the data 11 is a conversionmatrix or a conversion LUT for converting device RGB (or CMYK) values toXYZ (or Lab) values under a viewing condition of the data source side,the data 11 may be stored in the profile without further processing,thereby forming a profile dependent on the viewing condition of the datasource side.

[Generating Profile Dependent on Viewing Condition in Data DestinationSide]

Data of the LUT 132 and 133 shown in FIG. 12 for performing the gamutmapping process in the JCH and QMH color spaces, which are dependent ona viewing condition of the data destination side, and data 16 for aconversion LUT, which is dependent on a viewing condition of the datadestination side, are generated based on the profile which has beengenerated from a colorimetric value employing D50 or D65 as a reference,by the processing similar to the processing of the gamut mappingportions 44 and 45 and data generation portion 47 shown in FIG. 3.

Since the input/output color space for the data of the LUT 132 is in theJCH color space, the input color space must be XYZ (or Lab) values whichbase upon a viewing condition of the data destination side. To generatea conversion LUT for converting XYZ values under the viewing conditionof the data destination side to CMYK (RGB) values for a device, CMYKvalues for the device, which correspond to the input XYZ values underthe viewing condition of the data destination side, are obtained. Inother words, XYZ values under the viewing condition of the datadestination side are converted to color perception values JCH under theviewing condition of the data destination side by the color appearancemodel forward conversion, then compressed in the JCH color space by thedata of the LUT 132. Then, the color perception values JCH are convertedback to XYZ values under the viewing condition of the data destinationside by the color appearance model inverse conversion, and conversionbased on the data of the LUT 134 is performed. By this, CMYK values fora desired device are obtained. A conversion LUT can be generated bysequentially obtaining LUT grid points.

Similarly, since the input/output color space for the data of the LUT133 is in the QMH color space, the input color space must be XYZ valueswhich base upon a viewing condition of the data destination side. Togenerate a conversion LUT for converting XYZ values under the viewingcondition of the data destination side to CMYK values for a device, CMYKvalues for the device, which correspond to the input XYZ values underthe viewing condition of the data destination side, are obtained. Inother words, XYZ values under the viewing condition of the datadestination side are converted to color perception values QMH under theviewing condition of the data destination side by the color appearancemodel forward conversion, then compressed in the QMH color space by thedata of the LUT 133. Then, the color perception values QMH are convertedback to XYZ values under the viewing condition of the data destinationside by the color appearance model inverse conversion, and conversionbased on the data o the LUT 134 is performed. By this, CMYK values for adesired device are obtained. A conversion LUT can be generated bysequentially obtaining LUT grid points.

The LUT 132 is used in relative color matching, while the LUT 133 isused in absolute color matching. By storing these LUTs in a singleprofile, a profile which is dependent on the viewing condition of thedata destination side can be generated. Herein, a plurality of LUTs forrelative color matching can be produced and stored by the gamut mappingmethod (lightness preservation, chroma preservation or the like) in theJCH color space. Similarly, a plurality of LUTs for absolute colormatching can be produced and stored by the gamut mapping method(brightness preservation, colorfulness preservation or the like) in theQMH color space.

[Executing Color Matching]

In the color matching using a profile dependent on a viewing condition,the gamut mapping process is included in the profile in the datadestination side. Therefore, the gamut mapping in JCH color space or QMHcolor space does not need to be performed as described in each of theforegoing embodiments.

Color matching using a profile dependent on a viewing condition isdescribed with reference to FIGS. 2, 13 and 16.

Input color signals are converted from device-dependent RGB (or CMYK)values to XYZ (or Lab) values under the viewing condition of the datasource side, by the profile dependent on the viewing condition of thedata source side.

Next, XYZ values under the viewing condition of the data source side areconverted to JCH color space or QMH color space by the color appearancemodel forward conversion, and then converted back to XYZ values underthe viewing condition of the data destination side by the colorappearance model inverse conversion. Herein, selection of the JCH or QMHcolor space is determined by the gamut mapping mode. In a case ofrelative color matching, JCH color space is selected, while in a case ofabsolute color matching, QMH color space is selected. Furthermore, theconversion from XYZ values to JCH or QMH color space applies the viewingcondition of the data source side, such as the white point of anilluminant, an illuminance level or luminance level, and the state ofambient light, stored in the profile in the data source side. In theinverse conversion, the viewing condition of the data destination side,such as the white point of an illuminant, an illuminance level orluminance level, and the state of ambient light, stored in the profilein the data source side, is employed. The converted XYZ (or Lab) valuesunder the viewing condition of the data destination side are convertedto the device CMYK (or RGB) values by the profile dependent on theviewing condition of the data destination side.

As has been described above, the color matching processing using aprofile dependent on a viewing condition according to the fourthembodiment is equivalent to the color matching processing in the firstto third embodiments.

<Fifth Embodiment>

In each of the foregoing embodiments, a profile dependent on a viewingcondition is generated from one type of colorimetric value stored inadvance in a profile. However, in order to improve matching precision,it is better that colorimetric data for plural illuminants are stored inthe profile, then colorimetric data which is closest to the actualviewing condition is selected from the plural colorimetric data andconverted to colorimetric data corresponding to the actual viewingcondition, and a profile dependent on the viewing condition isgenerated.

FIG. 20 is a conceptual view of a profile 191 storing XYZ values of awhite point under different illuminants, device-dependent RGB values ofa color target, and XYZ values corresponding to the color target underrespective illuminants.

The color target serves as, for instance, a color target of IT8 definedby ANSI in a case of an input device, and serves as, for instance, 9×9×9RGB color patches in a case of an output device. For instance, referencenumeral 192 denotes RGB values of a color target and XYZ values underilluminant A (109.85, 100.0, 35.58); 193, RGB values of a color targetand XYZ values under illuminant D65 (95.05, 100.0, 108.88); 194, RGBvalues of a color target and XYZ values under illuminant D50 (96.42,100.0, 82.49); and 195, RGB values of a color target and XYZ valuesunder illuminant F2 (99.20, 100.0, 67.40). XYZ values of a color targetunder different illuminants as mentioned above can be obtained from aspectral distribution of each illuminant and a spectral reflectance ofeach color target. Therefore, instead of each of the XYZ values, thespectral distribution of each illuminant and spectral reflectance ofeach color target may be stored in the profile 191. Herein, if the colortarget used in each profile is fixed, RGB values of each color targetand data for spectral reflectance are common for each illuminant.Therefore, data related to the color target can be shared in each of theilluminants.

FIG. 21 shows a spectral distribution of a standard illuminant, whereinreference numeral 201 denotes a spectral distribution for the illuminantA, and reference numeral 202 denotes a spectral distribution forilluminant D65. By measuring a spectral distribution of an illuminant inan actual viewing condition, it is possible to generate a profiledependent on a viewing condition with better precision.

As shown in FIG. 20, in a case where XYZ values under a plurality ofstandard illuminants, such as the illuminants A, D65, D50, and F2, arestored in the profile, XYZ values under a standard illuminant which isclosest to the actual viewing condition are converted to XYZ values forthe viewing condition. To select the XYZ values under an illuminantclosest to the viewing condition, a search is performed utilizing theXYZ values of a white point under illuminants, which have been stored inthe profile. For instance, assuming that the white point under eachilluminant is XwYwZw, the chromaticity (xw, yw) can be obtained byequation (7).

$\begin{matrix}\left. \begin{matrix}{{xw} = \frac{Xw}{{Xw} + {Yw} + {Zw}}} \\{{yw} = \frac{Yw}{{Xw} + {Yw} + {Zw}}}\end{matrix} \right\} & (7)\end{matrix}$

Similarly, the chromaticity (x, y) of the white point under the viewingcondition is obtained by equation (8). A distance dw from a white pointunder each illuminant to a white point under a viewing condition isevaluated by, for instance, equation (9).

$\begin{matrix}\left. \begin{matrix}{x = \frac{X}{X + Y + Z}} \\{y = \frac{Y}{X + Y + Z}}\end{matrix} \right\} & (8) \\{{dw} = \sqrt{\left( {x - {xw}} \right)^{2} + \left( {y - {yw}} \right)^{2}}} & (9)\end{matrix}$

From the above calculation result, colorimetric data which is closest tothe actual viewing condition is selected, thereby obtaining XYZ valueswhich base upon the viewing condition, with better precision. Herein,the method similar to the above-described embodiments is used to convertXYZ values stored in the profile to XYZ values which base upon a viewingcondition. The XYZ values of the colorimetric illuminant reference areconverted to the color perception space JCH by the color appearancemodel based on a colorimetric condition, and then converted back to XYZvalues based on a viewing condition different from the colorimetriccondition. In a case where the distance dw from a white point under eachilluminant to a white point under the viewing condition is zero, thecolorimetric data may be used as the XYZ values for the viewingcondition. Besides this, the distance may be evaluated by a differencebetween a color temperature Tw of a white point under each illuminantand a color temperature T of a white point under a viewing condition.

FIG. 22 is a flowchart showing the process of conjecturing acolorimetric value from the colorimetric data for plural illuminants.Herein, step S211 in FIG. 22 corresponds to step S44 in FIG. 4, step S54in FIG. 5, step S64 in FIG. 6, step S74 in FIG. 7, step S144 in FIG. 14,step S154 in FIG. 15, and step S174 in FIG. 17.

[Caching Profile Data Dependent on Viewing Condition]

As mentioned above, because the processing for generating a profiledependent on a viewing condition is relatively complicated, it is timeconsuming to perform calculation each time color matching or the like isexecuted. In the normal usage state, once the viewing conditions of thedata source side and the data destination side are set, it is often thecase that users do not change the setting. Therefore, by caching a LUTor the like for mutually converting a device-independent color space toa device-dependent color space under a viewing condition, it is possibleto improve the processing efficiency.

Since the viewing condition can be set independently for the data sourceside and data destination side, the LUT for mutually converting adevice-independent color space to a device-dependent color space under aviewing condition is cached for each profile. The LUT is cached in eachprofile or other cache files. A LUT corresponding to the current viewingcondition may be cached, or a LUT corresponding to plural viewingconditions may be cached in unit of each viewing condition.

For instance, in a case of using ICC profile, a LUT for a viewingcondition, which corresponds to AtoBx Tag, BtoAx Tag, Gamut Tag or thelike in each profile, is stored as a private tag.

FIG. 23 shows an example in which a LUT, provided for mutuallyconverting a device-independent color space which bases upon a viewingcondition to a device-dependent color space, is stored in the ICCprofile. In the profile 221 including the cached LUT, AtoB0 Tag 222,AtoB1 Tag 223, AtoB2 Tag 224, BtoA0 Tag 225, BtoA1 Tag 226, BtoA2 Tag227, and gamut Tag 228 are stored as a public tag. Herein, the LUTstored as a public tag is provided for mutually converting adevice-independent color space employing D50 reference to adevice-dependent color space. Furthermore, the profile 228 includes, asa private tag, LUTs 229 to 2215 which correspond to public tags 222 to227, for mutually converting a device-independent color space whichbases upon a viewing condition to a device-dependent color space. In theprivate tag, a viewing condition 2216 at the time of caching is storedindependently of the cached LUT.

FIG. 24 is a flowchart showing caching processing. The processingdescribed hereinafter is an independent process for the data source sideand for the data destination side.

First, a viewing condition VC is obtained by user setting or the like.Next, cached LUT's viewing condition VC0 is obtained from a profile 232.The viewing condition VC is compared with the viewing condition VC0 interms of, for instance, a white point of an illuminant. If a match isfound between the viewing conditions, it is determined that the viewingcondition is the same as the condition where the last time an LUT iscached. Thus, the cached LUT is used for color matching or the like. Onthe other hand, if a match is not found between the viewing conditions,a LUT necessary for color matching is generated based on the viewingcondition.

The method of generating a LUT which is dependent on a viewing conditionis the same as the method described with reference to FIGS. 4, 6, 7, 12and 13. For the data source side, the conversion LUT 11 shown in FIG. 12is cached, while for the data destination side, a LUT combining the LUT132 and conversion LUT 16 shown in FIG. 12 is cached (i.e., equivalentto the conversion LUT 21 or 26 shown in FIG. 13). The viewing conditionat the time of LUT generation and the LUT which is dependent on theviewing condition are used for color matching or the like, and thenstored as a private tag in the profile.

According to each of the above-described embodiments, the followingeffects are achieved.

(1) Different viewing conditions (white point of an ambient light,illumination level and so on) can be set for each of the image datasource side and the image data destination side. By this, for instance,color reproduction under an environment of a remote place connected by anetwork can be simulated.

(2) XYZ values employing an ambient light in the image data source sideas a reference are converted by a human color appearance model to theJCH color space or QMH color space based on a viewing condition of theimage data source side (white point of an ambient light, illuminationlevel and so on), and then converted back to XYZ values employing anambient light in the image data destination side as a reference, basedon a viewing condition of the image data destination side (white pointof an ambient light, illumination level and so on). By this, colormatching can be performed with independent setting of viewing conditionsof the image data source side and image data destination side.

(3) Gamut-mapping is performed in the QMH (or JCH) color space, which isthe human color perception space. By virtue of this, human colorperception characteristics, such as the contour lines of hue, can bereflected upon the gamut mapping, and color matching most appropriatefor the ambient light can be performed.

(4) Color matching can be selected from two modes: absolute colormatching where the gamut mapping is performed in QMH color space, andrelative color matching where the gamut mapping is performed in JCHcolor space. By virtue of this, it is possible to attempt color matchingwhich is as absolute as possible in the color reproduction range of theoutput device, or attempt relative color matching which takes the bestadvantage of the dynamic range of the color reproduction range of theoutput device, thereby performing color matching most appropriate forthe color reproduction range of the output device.

(5) Colorimetric values (XYZ or Lab values) of a color target or colorpatch are converted to values in the JCH color space by a human colorappearance model based on a colorimetric condition (white point of acolorimetric illuminant or illumination level and so on), and thenconverted back to XYZ (or Lab) values based on a viewing condition(white point of an ambient light and illumination level and so on). Bythis, XYZ values employing the colorimetric illuminant as a referenceare converted to XYZ values employing an ambient light as a reference.

(6) Data indicative of a relation between device-independent data,obtained by colorimetry of a color target under a standard illuminant,and device-dependent data, which is dependent on a device into which thecolor target data is inputted, is stored in an input profile. Inaccordance with a viewing condition (white point of an ambient light,illumination level and so on) at the time of viewing an image to beinputted, a conversion matrix or a conversion LUT for convertingdevice-dependent data to device-independent data is dynamicallygenerated. By this, color matching corresponding to the ambient light atthe time of viewing the image to be inputted can be performed.Furthermore, the conversion matrix or conversion LUT for convertingdevice-dependent data stored in the input profile to device-independentdata (standard illuminant reference) is dynamically updated inaccordance with a viewing condition at the time of viewing the image tobe inputted (white point of an ambient light, illumination level and soon). By this, color matching corresponding to the ambient light at thetime of viewing the image to be inputted can be performed.

(7) A conversion matrix or a conversion LUT for convertingdevice-dependent data stored in a monitor profile to device-independentdata (white point reference of a monitor or standard illuminantreference) is dynamically updated in accordance with a viewing conditionof a monitor (white point of an ambient light, luminance level and soon). By this, color matching corresponding to an ambient light of amonitor can be performed.

(8) Data indicative of a relation between device-dependent data of acolor patch and device-independent data obtained by colorimetry of aprintout of the color patch under a standard illuminant, is stored in anoutput profile. In accordance with a viewing condition (white point ofan ambient light, illumination level and so on) at the time of viewingthe printout, a conversion LUT for converting device-independent data todevice-dependent data is dynamically generated. By this, color matchingcorresponding to an ambient light at the time of viewing an outputoriginal can be performed.

<Sixth Embodiment>

Described in a sixth embodiment is an example of a Graphic UserInterface (GUI) for manually setting a viewing condition (e.g., viewingcondition 1 or 2 in FIG. 2) for each of the foregoing embodiments.

FIG. 25 shows a GUI 191 for setting a parameter of a viewing conditionaccording to the sixth embodiment.

Reference numeral 192 denotes a text box for inputting a luminance of aviewing subject at the time of viewing an input; 193, a drop-downcombo-box for selecting the type of white point in the viewing subjectat the time of viewing an input; 194, a drop-down combo-box forselecting a viewing condition at the time of viewing an input; 195, atext box for inputting a chromatic adaptability at the time of viewingan input; 196, a text box for inputting a luminance of a viewing subjectat the time of viewing an output; 197, a drop-down combo-box forselecting a white point in the viewing subject at the time of viewing anoutput; 198, a drop-down combo-box for selecting a viewing condition atthe time of viewing an output; and 199, a text box for inputting achromatic adaptability at the time of viewing an output.

Note that the luminance relates to the luminance LA in the CIE CAM97sshown in FIG. 19; an illuminant relates to XwYwZw; an ambient lightrelates to the constant c, factor Nc, lightness contrast factor FLL andfactor for degree of adaptation F; and an adaptability relates to thevariable D. Although the variable D is obtained by LA and F according tothe CIE CAM97s in FIG. 19, the variable D according to the sixthembodiment is controlled manually.

Normally, about 20% of a white point is inputted as a luminance of aviewing subject. To obtain the type of white point in the viewingsubject, XYZ values of a white point in the viewing subject arenecessary. However, for a simple explanation, it is assumed herein thatthe reflectivity of a white point in the medium used is 100%, andtherefore, a white point of an illuminant is used herein. Furthermore,although it is better to utilize a white point of the illuminant underthe actual viewing condition, it is assumed herein that a standardilluminant type is selected. As the type of standard illuminant, thereare illuminants A, C, D65, D50, D93, F2, F8, and F11. Since an image isthe viewing subject herein, a relative luminance of the background isassumed to be 20%. With respect to the viewing condition, if a relativeluminance of the ambient is equal to or larger than 20%, which has beenassumed as the background relative luminance, the subject is determinedas “average surround”. If the ambient relative luminance is less than20%, the subject is determined as “dim”. If the ambient relativeluminance is almost 0%, the subject is determined as “dark”. Withrespect to the chromatic adaptability, the value is adjusted such that1.0 attains complete adaptation and 0.0 attains no adaptation.

<Seventh Embodiment>

For setting a parameter of a viewing condition as described in the sixthembodiment, values must be directly inputted. Therefore, handling theGUI is extremely difficult for general users who are not an colorexpert. In the seventh embodiment, the GUI 191 described in the sixthembodiment is improved for the ease of use.

The characteristic configuration of the seventh embodiment is asfollows.

(1) Parameter setting display is changed according to a user's level.

(2) A user can adjust the chromatic adaptability by designating a spacebetween a viewing subject of a data source side and a viewing subject ofa data destination side.

(3) A user can adjust the balance of the chromatic adaptability betweenthe viewing subject of a data source side and a viewing subject of adata destination side.

(4) A user can adjust an absolute chromatic adaptability whilemaintaining the balance of the chromatic adaptability between theviewing subject of a data source side and a viewing subject of a datadestination side.

FIG. 26 shows a GUI 201 which enables setting of a user level. FIG. 26shows the state in which “general user” is set as a user level. In theGUI 201, a user does not need to directly input a parameter, but is ableto set all the viewing conditions by making selection or adjusting aslide bar. The contents of selections are expressed in a user-friendlymanner.

Referring to FIG. 26, reference numeral 202 denotes a drop-downcombo-box for selecting a user level; 203, a drop-down combo-box forselecting a viewing subject at the time of viewing an input; 204, adrop-down combo-box for selecting a luminance level in the viewingsubject at the time of viewing the input; 205, a drop-down combo-box forselecting the type of white point in the viewing subject at the time ofviewing the input; 206, a drop-down combo-box for selecting a viewingcondition at the time of viewing the input; 207, a drop-down combo-boxfor selecting a viewing subject at the time of viewing an output; 208, adrop-down combo-box for selecting a luminance level in the viewingsubject at the time of viewing the output; 209, a drop-down combo-boxfor selecting the type of white point in the viewing subject at the timeof viewing the output; 2010, a drop-down combo-box for selecting aviewing condition at the time of viewing the output; 2011, an iconindicative of the viewing subject at the time of viewing an input withthe set viewing spacing; and 2012, an icon indicative of the viewingsubject at the time of viewing an output with the set viewing spacing.

The displayed user level is switched, for instance, as shown in FIG. 27,by designating the drop-down combo-box 202 for selecting a user level.Items of selectable viewing subject include “monitor”, “originaldocument”, “printout” and so forth, and depending on the selected item,items of selection menu and values set according to the item vary. Itemsof selectable luminance level for the viewing subject include “bright”,“relatively light”, “average”, “relatively dark”, which are expressed inthe intuitive manner for general users. Also, items of selectable whitepoint in the viewing subject do not include expressions for expert userssuch as D93 or F2 or the like, but include expressions for generalusers, such as “bluish white”, “white”, and “yellowish white” for amonitor, and “white fluorescent light”, “neutral white fluorescentlight”, “incandescent light”, “clear weather in the open air”, “overcastweather in the open air” for an original document or printout.

For setting a viewing space, the space between the viewing subjects isadjusted by operating the slide bar, for instance, for comparing amonitor and a printout placed next to each other, or comparing thesubjects placed apart from each other. The setting concerns withdetermination of a chromatic adaptability. The viewing subjects areexpressed by icons so that a user can intuitively adjust the distancebetween the icons by using a slide bar.

The chromatic adaptability is defined by the following equationaccording to CIE CAM97s.

complete   adaptation:D = 1.0 no   adaptation:D = 0.0${\text{incomplete~~~adaptation:}D} = {F - \frac{F}{1 + {2 \cdot {LA}^{\frac{1}{4}}} + \frac{{LA}^{2}}{300}}}$

Herein, D indicates the chromatic adaptability. F indicates a constantwhich varies in accordance with a viewing condition, wherein F is 1.0 inthe average surround and 0.9 in the dim or dark condition. La indicatesa luminance in the viewing subject. The chromatic adaptability D can beset independently for the input side and output side.

In the present embodiment, the chromatic adaptability at the time ofviewing an input and output is defined such that the chromaticadaptability is changed in accordance with the space (viewing distance)between the viewing subject in the input side and the viewing subject inthe output side. Assuming that the complete adaptation is most closelyachieved when the viewing distance is infinite, the chromaticadaptability can be defined by the following equation.

${{Ds0} = {{Fs} - \frac{F}{1 + {2 \cdot {LA}^{\frac{1}{4}}} + \frac{{LAs}^{2}}{300}}}}\mspace{85mu}$${{Dd0} = {{Fd} - \frac{Fd}{1 + {2 \cdot {LA}^{\frac{1}{4}}} + \frac{{LAd}^{2}}{300}}}}\mspace{79mu}$Ds = Ds0 ⋅ VD + Ds0 ⋅ VD0 ⋅ (1.0 − VD)Dd = Dd0 ⋅ VD + Dd0 ⋅ VD0 ⋅ (1.0 − VD) 

Herein, Ds0 indicates a chromatic adaptability at the time of viewing aninput, which is determined by the luminance level and viewing condition.Fs indicates a constant which varies in accordance with the viewingcondition at the time of viewing the input. LAs indicates a luminance ina viewing subject at the time of viewing the input. Dd0 indicates achromatic adaptability at the time of viewing an output, which isdetermined by the luminance level and viewing condition. Fd indicates aconstant which varies in accordance with the viewing condition at thetime of viewing the output. LAd indicates a luminance in a viewingsubject at the time of viewing the output. Ds indicates a chromaticadaptability at the time of viewing an input, which is determined by theviewing distance, luminance level, and viewing condition. Dd indicates achromatic adaptability at the time of viewing an output, which isdetermined by the viewing distance, luminance level, and viewingcondition. VD indicates the position of a slide bar indicative of aviewing distance, wherein if the viewing distance is zero, VD takes theminimum value 0.0, while if the viewing distance is infinity, VD takesthe maximum value 1.0. VD0 indicates a constant for determining achromatic adaptability when the viewing distance is zero.

FIG. 27 shows a GUI 211 in a case where the user level is set in the“professional” level. Since the GUI is for expert users, parameters canbe inputted directly, and items are expressed by technical expressions.

Herein, reference numeral 2111 denotes a static text for displaying avalue of a chromatic adaptability as a viewing condition at the time ofviewing an input; 2112, a static text for displaying a value of achromatic adaptability as a viewing condition at the time of viewing anoutput; 2113, a slide bar for adjusting the balance of a chromaticadaptability between a viewing subject in the input side and a viewingsubject in the output side; and 2114, a slide bar for adjusting anabsolute chromatic adaptability while maintaining the balance of thechromatic adaptability between the viewing subject in the input side andthe viewing subject in the output side.

The chromatic adaptability in the input side and output side is definedas follows so as to be adjustable by the balance and absolute intensity.

Ds0 = 1.0 − BL Dd0 = BL${Ds} = {\frac{Ds0}{{MAX}\left( {{Ds0},{Dd0}} \right)} \times {VL}}$${Dd} = {\frac{Dd0}{{MAX}\left( {{Ds0},{Dd0}} \right)} \times {VL}}$

Herein, Ds0 indicates a chromatic adaptability at the time of viewing aninput, which is determined by the balance adjustment of the chromaticadaptability. Dd0 indicates a chromatic adaptability at the time ofviewing an output, which is determined by the balance adjustment of thechromatic adaptability. BL indicates the position of a slide barindicative of a balance, wherein if the balance at the time of viewingan input is 100%, BL takes the minimum value 0.0, and if the balance atthe time of viewing an output is 100%, BL takes the maximum value 1.0,and the center is 0.5. Ds indicates a chromatic adaptability at the timeof viewing an input, which is determined by the balance of the chromaticadaptability and absolute intensity adjustment. Dd indicates a chromaticadaptability at the time of viewing an output, which is determined bythe balance of the chromatic adaptability and absolute intensityadjustment. VL indicates the position of a slide bar indicative of anabsolute intensity, wherein if the intensity is zero, VL takes theminimum value 0.0, and if the intensity is maximum, VL takes the maximumvalue 1.0. Note that MAX( ) indicates the selection of the maximum valuein the parenthesis.

The balance is adjusted such that the complete adaptation is attainedwhen the balance intensity is large. Then, the balance intensity adjuststhe entire chromatic adaptability while maintaining the balance. Inother words, if the balance is set in the center and the absoluteintensity is set to the maximum value, the chromatic adaptability in theinput side and output side both attains complete adaptation.

The present invention can be applied to a system constituted by aplurality of devices (e.g., host computer, interface, reader, printer)or to an apparatus comprising a single device (e.g., copying machine,facsimile machine).

Further, the object of the present invention can also be achieved byproviding a storage medium storing program codes for performing theaforesaid processes to a computer system or apparatus (e.g., a personalcomputer), reading the program codes, by a CPU or MPU of the computersystem or apparatus, from the storage medium, then executing theprogram.

In this case, the program codes read from the storage medium realize thefunctions according to the embodiments, and the storage medium storingthe program codes constitutes the invention.

Further, the storage medium, such as a floppy disk, a hard disk, anoptical disk, a magneto-optical disk, CD-ROM, CD-R, a magnetic tape, anon-volatile type memory card, and ROM can be used for providing theprogram codes.

Furthermore, besides aforesaid functions according to the aboveembodiments are realized by executing the program codes which are readby a computer, the present invention includes a case where an OS(operating system) or the like working on the computer performs a partor the entire processes in accordance with designations of the programcodes and realizes functions according to the above embodiments.

Furthermore, the present invention also includes a case where, after theprogram codes read from the storage medium are written in a functionexpansion card which is inserted into the computer or in a memoryprovided in a function expansion unit which is connected to thecomputer, CPU or the like contained in the function expansion card orunit performs a part or the entire process in accordance withdesignations of the program codes and realizes functions of the aboveembodiments.

The present invention is not limited to the above embodiments andvarious changes and modifications can be made within the spirit andscope of the present invention. Therefore, to appraise the public of thescope of the present invention, the following claims are made.

1. An image processing method for performing a color process based on a color appearance model, said method comprising the steps of: using a user interface, inputting space information, which represents a space between locations of a viewing subject at a data source side and a viewing subject at a data destination side, based on an instruction of a user entered through the user interface, in which the space information is adjusted by comparing a monitor and a printer placed next to each other or apart from each other so that the user is able to make a determination of chromatic adaptability; setting a parameter of a viewing condition based on the inputted space information; and performing the color process based on the color appearance model by using the set parameter.
 2. The method according to claim 1, wherein the parameter includes a chromatic adaptability condition.
 3. The method according to claim 1, further comprising the step of inputting plural items of viewing information which relate to a viewing condition of the data source side and a viewing condition of the data destination side.
 4. The method according to claim 1, wherein the color process comprises color matching processing based on profiles of the data source side and the data destination side.
 5. The method according to claim 1, in which the space information is adjusted by operating a slide bar.
 6. An image processing method comprising the steps of: using a user interface for manually inputting space information which represents a space between locations of a viewing subject at a data source side and a viewing subject at a data destination side, in which the space information is adjusted by comparing a monitor and a printer placed next to each other or apart from each other so that the user is able to make a determination of chromatic adaptability; using a user interface for manually inputting viewing information which relates to a viewing condition, for performing color process on input image data based on a color appearance model; setting a parameter of viewing condition based on the inputted space information and viewing information; and performing the color process based on the color appearance model by using the set parameter.
 7. The method according to claim 6, in which the space information is adjusted by operating a slide bar.
 8. An image processing apparatus for performing a color process based on a color appearance model, said apparatus comprising: an inputting section, arranged to input space information which represents a space between locations of a viewing subject at a data source side and a viewing subject at a data destination side, based on an instruction of a user using a user interface, wherein the space information is adjusted by comparing a monitor and a printer placed next to each other or apart from each other so that the user is able to make a determination of chromatic adaptability; a setter, arranged to set a parameter of viewing condition based on the inputted space information; and a processor, arranged to perform the color process based on the color appearance model by using the set parameter.
 9. The apparatus according to claim 8, wherein the parameter includes a chromatic adaptability condition.
 10. The apparatus according to claim 8, wherein said inputting section farther inputs plural items of viewing information which relate to a viewing condition of the data source side and a viewing condition of the data destination side.
 11. The apparatus according to claim 8, wherein the color process comprises color matching processing based on profiles of the data source side and the data destination side.
 12. The apparatus according to claim 8, wherein the space information is adjusted by operating a slide bar.
 13. A computer program product comprising a computer readable medium storing computer program codes, for an image processing method performing a color process based on a color appearance model, said product comprising process procedure codes for: using a user interface, inputting space information which represents a space between locations of a viewing subject at a data source side and a viewing subject at a data destination side, in which the space information is adjusted by comparing a monitor and a printer placed next to each other or apart from each other so that the user is able to make a determination of chromatic adaptability; setting a parameter of viewing condition based on the inputted space information; and performing the color process based on the color appearance model by using the set parameter.
 14. A computer program product comprising a computer readable medium storing computer program codes, for an image processing method performing a color process on input image data based on a color appearance model, said product comprising process procedure codes for: realizing a user interface to manually input space information which represents a space between locations of a viewing subject at a data source side and a viewing subject at a data destination side, in which the space information is adjusted by comparing a monitor and a printer placed next to each other or apart from each other so that the user is able to make a determination of chromatic adaptability; realizing a user interface to manually input viewing information which relates to a viewing condition; setting a parameter of viewing condition based on the inputted space information and viewing information; and performing the color process based on the color appearance model by using the set parameter. 